loadXml reports an error instead of throwing an exception when the xml is not well formed. This is annoying if you are trying to to loadXml() in a try...catch statement. Apparently its a feature, not a bug, because this conforms to a spefication.

If you want to catch an exception instead of generating a report, you could do something like

When using loadXML() to parse a string that contains entity references (e.g., &nbsp;), be sure that those entity references are properly declared through the use of a DOCTYPE declaration; otherwise, loadXML() will not be able to interpret the string.

Given the above code, PHP will issue a Warning about the entity 'nbsp' not being properly declared. Also, the call to saveXML() will return nothing but a trimmed-down version of the original processing instruction...everything else is gone, and all because of the undeclared entity.

Since the 'nbsp' entity is defined in the DOCTYPE, PHP no longer issues that Warning; the string is now well-formed, and loadXML() understands it perfectly.

You can also use references to external DTDs in the same way (e.g., <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN""http://www.w3.org/TR/html4/strict.dtd">), which is particularly important if you need to do this for many different documents with many different possible entities.

Also, as a sidenote...entity references created by createEntityReference() do not need this kind of explicit declaration.

The documentation states that loadXML can be called statically, but this is misleading. This feature seems to be a special case hack and its use seems to be discouraged according to http://bugs.php.net/bug.php?id=41398.

Calling the method statically will fail with an error if the code runs with E_STRICT error reporting enabled.

The documentation should be changed to make it clear that a static call is against recommended practice and won't work with E_STRICT.

While loadXML() expects its input to have a leading XML processing instruction to deduce the encoding used, there's no such concept in (non-XML) HTML documents. Thus, the libxml library underlying the DOM functions peeks at the <META> tags to figure out the encoding used.

Note that loadXML crops off beginning and trailing whitespace and linebreaks.

When using loadXML and appendChild to add a chunk of XML to an existing document, you may want to force a linebreak between the end of the XML chunk and the next line (usually a close tag) in the output file:

Although it is said that DOM should not be used to make 'pretty' XML output, it is something I struggled with to get something that was readable for testing. Another solution is to use the createDocumentFragment()->appendXML(..XML-Chunk..) instead, which seems not to trim off linebreaks like DOMDocument->loadXML() does.

Loading from a string works fine without the <?xml version="1.0" encoding="utf-8"?> header, but in this case the xmlEncoding won't be set, and this makes the utf-8 characters (international, and special characters) to be encoded as hexa entities when saved with saveXML()!